Richtek RT8452GQW, RT8452GS Schematic [ru]

Conceptual
RT8452
High Voltage High Current LED Driver Controller for Boost or Buck-Boost Topology
General Description
The RT8452 is a current mode PWM controller designed to drive an external MOSFET for high current LED applications. With a current sense amplifier threshold of 180mV, the LED current is programmable with one external current sense resistor and the power loss is minimized. With the maximum operating input voltage of 40V and output voltage up to 60V, the RT8452 is ideal for boost or buck-boost operation. (See RT8450 and RT8451 for buck mode LED driver application.)
With 1MHz operating frequency, the external inductor and capacitors can be small while mainteining high efficiency.
Dimming can be either analog or PWM digital. The unique built-in clampping comparator and filter allow easy low noise analog dimming conversion from PWM signal with only one external capacitor. PWM dimming control is made easy with a build in FET driver dedicated for the extermal dimming MOSFET.
The RT8452 is available in WQFN-16L 3x3 and SOP-16
packages.
Features
l High Voltage Capability : V
60V
l Boost or Buck-Boost Operation l Current Mode PWM with 1MHz Switching
Frenquency
l Easy Dimming : Analog, PWM Digital or PWM
Converting to Analog with One External Capacitor
l Programmable Soft Start to Avoid Inrush Current l Programmable Over Voltage Protection to Limit
Output Voltage
l V
Undervoltage Lockout and Thermal Shutdown
IN
l 16-Lead WDFN and SOP Packages. l RoHS Compliant and 100% Lead (Pb)-Free
Up to 40V, V
IN
OUT
Up to
Applications
l General Industrial High Power LED Lighting l Desk Lights and Room Lighting l Building and Street Lighting l Industrial Display Backlight
Ordering Information
RT8452
Package Type
S : SOP-16
QW : WDFN-16L 3x3 (W-Type) Operating Temperature Range
G : Green (Halogen Free with Commer­ cial Standard)
Note : Richtek Green products are :
}RoHS compliant and compatible with the current require-
}Suitable for use in SnPb or Pb-free soldering processes. }100% matte tin (Sn) plating.
Marking Information
For marking information, contact our sales representative directly or through a Richtek distributor located in your area, otherwise visit our website for detail.
Pin Configurations
(TOP VIEW)
GND
VCCENOVP
GBIAS
PWMOUT
PWMOUT
PWMDIM
1 2
GATE
ISW
GND
3 4
ISP
PWMDIM
WQFN-16L 3x3
GBIAS
GATE
ISW
ISP ISN
2 3 4 5 6 7
VCACTL
SOP-16
13141516
12
NC
11
SS
10
DCTL
17
9
ACTL
8765
VC
ISN
16
GND
15
VCC
14
OVP
13
EN
12
NC
11
SS
10
DCTL
98
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RT8452
Typical Application Circuit
V
Analog
Dimming
R1
10k
C2 3nF
R1
10k
C2 3nF
IN
5V
C3 10nF
Figure 1. Analog Dimming in Boost Configuration
V
IN
5V
C3 10nF
C4
4.5V to 40V
4.5V to 40V
PWM Dimming control
C1
15 13
10
11
C4
C1
C5
0.5uF
9
8
1
15 13
10
8
11
1
9
Conceptual
L
10uH
RT8452
VCC EN
ACTL DCTL
VC SS
GBIAS
VCC EN
DCTL
VC SS
GBIAS ACTL
PWMOUT
PWMDIM
GND
L
10uH
RT8452
PWMOUT
PWMDIM
GND
2
GATE
4
ISW
6
ISP
7
ISN
14
OVP
3 5
16, Exposed Pad (17)
2
GATE
4
ISW
6
ISP
7
ISN
14
OVP
3 5
16, Exposed Pad (17)
R3
R3
C5 1uF
R5
C6 1uF
R5
R4
R4
R2
180mV
R2
180mV
V
V
OUT
OUT
V
OUT
60V MAX
V
OUT
60V MAX
Figure 2. PWM to Analog Dimming in Boost Configuration
V
OUT
V
4.5V to 40V
R1
10k
C2 3nF
5V
L
VCC EN
ACTL DCTL VC
SS GBIAS
10uH
RT8452
GATE
ISW
ISP
ISN
PWMOUT
PWMDIM
OVP
GND
16, Exposed Pad (17)
14
2 4
6 7 3
5
R3
IN
C1
15 13
9
10
8
11
C3 10nF
1
C4
C5 1uF
R5
180mV
R4
R2
V
OUT
60V MAX
Figure 3. True PWM Dimming in Boost Configuration
DS8452-02C March 2008www.richtek.com
2
Sense Pin. Connect the current
V
4.5V to 40V
IN
5V
Analog
Dimming
R1
10k
C2 3nF
C3 10nF
C1
C4
Figure 4. Analog Dimming in Buck-Boost Configuration
Functional Pin Description
15 13
9
10
8
11
1
Conceptual
RT8452
VCC EN
ACTL DCTL
VC SS
GBIAS
PWMOUT
PWMDIM
GND
L
10uH
2
GATE
4
ISW
7
ISN
6
ISP
3 5 14
OVP
16, Exposed Pad (17)
R3
R5
R4
C5 1uF
R2
180mV
V
OUT
V
OUT
60V MAX
RT8452
SOP-16 QFN3X3-16 Pin Name
Pin Function
1 1 GBIAS The Internal Gate Driver Bias Pin.A good bypass capacitor is required. 2 2 GATE The External MOSFET Switch Gate Driver Output Pin. 3 3 PWMOUT The Output Pin for the PWM Dimming FET Driver.
4 4 ISW
The External MOSFET Switch Current
sense resistor between external N-MOSFET switch and the ground.
5 5 PWMDIM The Control Input Pin for the PWM Dimming FET Driver. 6 6 ISP The LED Current Sense Amplifier Positive Input.
7 7 ISN
The LED Current Sense Amplifier Negative Input. Voltage
threshold between ISP and ISN is 180mV.
8 8 VC The PWM Control Loop Compensation Pin. 9 9 ACTL
The Analog Dimming Control Pin. The effective programming
voltage range of the pin is between 0.3V and 1.2V.
By adding a 0.1uF filtering capacitor on ACTL pin, the PWM dimming
10 10 DCTL
11 11 SS
signal on DCTL pin can be averaged and converted into analog
dimming signal on the ACTL pin following the formula below.
V
= 1.2V x PWM Dimming Duty Cycle.
ACTL
The Soft-Start Pin. A capacitor of at least 10nF is required for proper
soft start.
12 12 NC No Internal Connection. 13 13 EN
14 14 OVP
The Chip Enable (Active High) Pin. When this pin voltage is low, the
chip is in shutdown mode. The Over Voltage Protection Pin. The PWM converter turns off when The voltage of the pin goes higher than 1.2V.
15 15 VCC
16
16
Exposed Pad (17)
DS8452-02C March 2008www.richtek.com
GND
The Power Supply Pin of the Chip. For good bypass, a low ESR Capacitor is required.
The Ground Pin. The exposed pad must be soldered to a large PCB And connected to GND for maximum power dissipation.
3
RT8452
Function Block Diagram
Conceptual
EN
VCC
OVP
VC
SS
DCTL
1.4V
4.5V
1.2V
1.2V
+
-
6uA
+
-
­+
+
-
Shutdown
-
ACTL
6V
OSC
+
GM
1.2V
+
-
100k
100mV
VCC
GBIAS GATE
5V
GBIAS
PWMOUT PWMDIM
ISW ISN
ISP
GND
+
-
S
R R R
R
­+
­+
V
ISP
180
– V
(mV)
0
ISN
0.31.2
Figure 5
V
ACTL
(V)
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Conceptual
Absolute Maximum Ratings (Note 1)
RT8452
l Supply Input Voltage, V l GBIAS, GATE, PWMDIM, PWMOUT, ISW--------------------------------------------------------------------10V l ISP, ISN----------------------------------------------------------------------------------------------------------------65V l DCTL, ACTL, OVP, EN---------------------------------------------------------------------------------------------20V l Power Dissipation, P
-----------------------------------------------------------------------------------------45V
CC
@ TA = 25°C
D
SOP-16----------------------------------------------------------------------------------------------------------------1.053W
WQFN-16L 3x3--------------------------------------------------------------------------------------------------------1.471W
l Package Thermal Resistance (Note 4)
SOP-16, θJC-----------------------------------------------------------------------------------------------------------95°C/W SOP-16, θJC----------------------------------------------------------------------------------------------------------45°C/W
WQFN-16L 3x3, θJA-------------------------------------------------------------------------------------------------68°C/W
WQFN-16L 3x3, θJC-------------------------------------------------------------------------------------------------7.5°C/W
l Junction Temperature-----------------------------------------------------------------------------------------------150°C l Lead Temperature (Soldering, 10 sec.)--------------------------------------------------------------------------260°C l Storage Temperature Range--------------------------------------------------------------------------------------- 65°C to 150°C l ESD Susceptibility (Note 2)
HBM (Human Body Mode)-----------------------------------------------------------------------------------------2kV MM (Machine Mode)------------------------------------------------------------------------------------------------200V
Recommended Operating Conditions (Note 3)
l Junction Temperature Range-------------------------------------------------------------------------------------- 40°C to 125°C l Ambient Temperature Range-------------------------------------------------------------------------------------- 40°C to 85°C
Electrical Characteristics
(VCC = 24V, No Load on any Output, T
Parameter Symbol Conditions Min Typ Max Unit
Overall
Supply Voltage V Supply Current I
Shutdown Current I Shutdown Threshold V
EN Input Current V
Current Sense Amplifier
Input Threshold (V
ISP
V
) 4.5V common mode 40V 170 180 190 mV
ISN
ISP / ISN Input Current I VC Output Current I VC Threshold for PWM Switch
Off
LED Dimming
= 25°C, unless otherwise specified)
A
4.5 -- 40 V
CC
VC 0.4V (Switching off) -- 4 6 mA
VCC
VEN 0.7V -- 12 -- uA
SHDN
-- 1.4 -- V
EN
5V -- -- 0.5 uA
EN
/ I
ISP
VC
ISN
4.5V V V
V
ISP
0.5V VC 2.4V
= V
ISP
= 120mV,
ISN
60V -- 140 -- uA
ISN
-- ±20 -- uA
-- 0.7 -- V
Analog Dimming ACTL Pin Input Current
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I
0.3V V
ACTL
1.3V -- -- 1 uA
ACTL
To be continued
5
RT8452
Parameter Symbol Conditions Min Typ Max Unit
Conceptual
LED Current Off Threshold at ACTL DCTL Input Current I
V
ACTL_Off
0.3V V
DCTL
-- 0.2 -- V 6V -- -- 0.5 uA
DCTL
PWM Control
Switching Frequency f Maximum Duty Cycle (Note 5)
800k
SW
1M 1.2M
Hz
-- 86 -- %
Minimum on Time -- 200 -- ns
Switch Gate Driver
GBIAS Voltage V Gate Voltage High V
Gate Voltage Low V
GBIAS
Gate_H
Gate_L
I
GBIAS
I
Gate
I
Gate
I
Gate
I
Gate
= 20mA -- 5.7 -- V = 50mA -- 4.2 -­= 100uA -- 5 -­= 50mA -- 0.25
--
= 100uA -- 0.1 --
V
V
GATE Drive Rise and Fall Time 1nF Load -- 15 -- ns PWM Switch Current Limit Threshold
I
SW_LIM
-- 100 -- mV
PWM Dimming Gate Driver
PWMDIM Threshold (Low to High)
-- 1.5 -- V
PWMDIM Threshold Hysteresis -- 0.5 -- V PWMOUT Drive Rise and Fall Time
1nF Load -- 40 -- ns
OVP and Soft Start
OVP Threshold V OVP Input Current I Soft Start Pin Current I
Note 1. Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.
These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Note 2. Devices are ESD sensitive. Handling precaution recommended. The human body model is a 100pF capacitor discharged
through a 1.5k resistor into each pin.
Note 3. The device is not guaranteed to function outside its operating conditions. Note 4. θJA is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of
JEDEC 51-7 thermal measurement standard.
Note 5. When the natural maximum duty cycle of 1MHz switching frequency is reached, the switching cycle will be skipped (not
reset) as the operating condition requires to effectively stretch and achieve higher on cycle than the natural maximum duty cycle set by the 1MHz switching frequency.
OVP SS
-- 1.2 -- V
OVP_th
0.7V V
V
2V -- 6 -- uA
SS
1.5V -- -- 0.1 uA
OVP
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Datasheet Revision History
Conceptual
RT8452
Version
00C 2008/2/22 first edition
01C 2008/2/27
02C 2008/3/18 Ordering Information Modify
Data Page No.
Item Description
Features Typical Application Circuit Functional Pin Description Function Block Diagram Electrical Characteristics
Modify
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RT8452
Outline Dimension
Conceptual
D
E
A
A3
A1
Symbol
A 0.700 0.800 0.028 0.031
Dimensions In Millimeters
D2
Min Max Min Max
SEE DETAIL A
1
E2
be
L
1 2
1 2
DETAIL A
Pin #1 ID and Tie Bar Mark Options
Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated.
Dimensions In Inches
A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010
b 0.180 0.300 0.007 0.012
D 2.950 3.050 0.116 0.120
D2 1.300 1.750 0.051 0.069
E 2.950 3.050 0.116 0.120
E2 1.300 1.750 0.051 0.069
e 0.500 0.020 L 0.350 0.450
0.014 0.018
W-Type 16L QFN 3x3 Package
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Conceptual
RT8452
J
I
Symbol
A
F
D
Dimensions In Millimeters
B
C
Dimensions In Inches
H
Min Max Min Max
M
A 9.804 10.008 0.386 0.394 B 3.810 3.988 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.508 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.178 0.254 0.007 0.010
I 0.102 0.254 0.004 0.010 J 5.791 6.198 0.228 0.244
M 0.406 1.270 0.016 0.050
Richtek Technology Corporation
Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
16–Lead SOP Plastic Package
Richtek Technology Corporation
Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
DS8452-03C December 2008www.richtek.com
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